OsLOX2, a rice type I lipoxygenase,confers opposite effects on seed germination and longevity

Rice production and seed storage are confronted with grain deterioration and loss of seed viability. Some members of the lipoxygenase (LOX) family function in degradation of storage lipids during the seed germination, but little is known about their influence on seed longevity during storage. We characterized the role of rice OsLOX2 gene in seed germination and longevity via over-expression and knock-down approaches. Abundant expression of OsLOX2 was detected in panicles, roots, and stems, but not in leaves. Moreover, OsLOX2 was highly induced during germination. OsLOX2 protein, located in the cytoplasm, showed a wide range of temperature adaptation (20–50 °C) and a substrate preference to linoleic acid. Lines over-expressing OsLOX2 showed accelerated seed germination under normal condition and lower seed viability after accelerated aging. RNA interference (RNAi) of OsLOX2 caused delayed germination and enhanced seed longevity. RNAi lines with strongly repressed OsLOX2 activity completely lost the capability of germination after accelerated aging. More lipid hydroperoxide were found in OE15 than the control, but less in RNAi lines than in the WT Nipponbare. Therefore, OsLOX2 acts in opposite directions during seed germination and longevity during storage. Appropriate repression of the OsLOX2 gene may delay the aging process during the storage without compromising germination under normal conditions.     

Molecular genetic characterization of rice seed lipoxygenase 3 and assessment of its effects on seed longevity

Lipoxygenases (LOXs) are enzymes involved in lipid peroxidation. Here we reported the identification, molecular and functional characterization of the gene encoding rice (Oryza sativa L.) seed LOX3 (sLOX3). Via a map-based cloning strategy we identified Os03g0700400 as the candidate gene encoding sLOX3. Further functional complementary test and biochemical characterization of the recombinant Os03g0700400 protein verified the identification. The sLOX3 gene was highly expressed in roots, moderately in embryos and very weakly in leaves, leaf sheaths and stems. Transient expression experiment (in rice protoplasts) and subsequent laser confocal microscopic analysis demonstrated that the sLOX3 protein was localized into the cytosol. We next showed that overexpression of sLOX3 in a japonica sLOX3-normal rice cultivar, Wuyunjing 7 accelerated the decrease of seed germination ability when the seeds were routinely stored, which demonstrated that sLOX3 had a negative effect on seed longevity (storability). Meanwhile, an increased occurrence of embryo decay was observed in the same transgenic seeds, suggesting that sLOX3 might negatively affect seed longevity by facilitating colonization of particular seed pathogens. Our result forwarded the understanding of the effects of 9-LOX on rice seed longevity.     

Mechanism underlying the retarded nuclear translocation of androgen receptor splice variants

As shown in our previous study, two alternatively spliced androgen receptor(AR) variants, which are exclusively expressed in the granulosa cells of patients with polycystic ovary syndrome, exhibit retarded nuclear translocation compared with wild-type AR. However, researchers have not yet determined whether these abnormalities correlate with heat shock protein 90(HSP90)and importin α(the former is a generally accepted co-chaperone of AR, and the latter is a component of classical nuclear import complexes). Here, these two variants were mainly retained in cytoplasm with HSP90 and importin α in the presence of dihydrotestosterone(DHT), and their levels in nucleus were significantly reduced, according to the immunofluorescence staining. The binding affinity of two AR variants for importin α was consistently decreased, while it was increased in WT-AR following DHT stimulation, leading to reduced nuclear import, particularly for the insertion-AR(Ins-AR). However, the binding affinities of two AR variants for HSP90 were increased in the absence of DHT compared with WT-AR, which functioned to maintain spatial structural stability, particularly for the deletion-AR(Del-AR). Therefore, the retarded nuclear translocation of two AR variants is associated with HSP90 and importin α, and the abnormal binding affinities for them play critical roles in this process.     

Association between the prevalence of hyperuricemia and reproductive hormones in polycystic ovary syndrome

Background

The prevalecne of hyperuricemia in polycystic ovary syndrome (PCOS) is still uncertain. We aimed to investigate the prevalence of hyperuricemia in PCOS and to determine the influence of reproductive hormones on uric acid concentration.

Methods

This retrospective cross-sectional study was performed at a large reproductive medicine center. Between March 2007 and October 2016, a total of 1,183 women with PCOS and 10,772 women without PCOS were included. PCOS was diagnosed according to the Rotterdam criteria. Anthropometric parameters, blood pressure, uric acid, reproductive hormones, glucose and lipids were measured in all subjects.

Results

The serum uric acid (SUA) level was higher in women with PCOS than in women without PCOS. The prevalence of hyperuricemia in women with PCOS (25.48%) was significantly higher than that in women without PCOS (8.74%). Analysis stratified for age and body mass index (BMI) showed that both the SUA level and the prevalence of hyperuricemia were higher in women with PCOS of different age and BMI groups than in women without PCOS. After adjusting for age, BMI and estimated glomerular filtration rate (eGFR), logistic regression analysis revealed that the luteinizing/follicle-stimulating hormone (LH/FSH) ratio (odds ratio (OR)?=?1.20, 95% CI?=?1.01–1.43) and testosterone level (OR?=?1.56, 95% CI?=?1.27–1.90) were positively associated with the prevalence of hyperuricemia in females with PCOS.

Conclusions

The serum uric acid (SUA) level and the prevalence of hyperuricemia markedly increased in women with PCOS. The testosterone level was positively associated with the SUA level and the prevalence of hyperuricemia in females with PCOS.